Stabilization of hot melt adhesives

ABSTRACT

The present invention pertains to a stabilized hot melt adhesive containing a) one or more hot melt adhesive materials and b) a stabilizer composition. The one or more hot melt adhesive materials a) include a polyolefin, a styrene-isoprene-styrene block co-polymer, a styrene-butadiene-styrene block co-polymer, a polyacrylate, an acryl-copolymer, an ethylene vinyl acetate, a polyamide, a polyester, a polyurethane, a polyimide, a silane terminated polyolefin, a silane terminated poly-ether, and a silane terminated polyurethane. The stabilizer composition includes two or three of a component (A) which is a specific sterically hindered amine, a component (B) which is a polymeric sterically hindered amine, and a component (C) which is a specific sterically hindered phenol.

The present invention pertains to a stabilized hot melt adhesivecomprising a) one or more hot melt adhesive materials selected from thegroup consisting of polyolefins such as amorphous poly-alpha-olefins,metallocene based polyolefins, styrene-isoprene-styrene (SIS) blockcopolymer, styrene-butadiene-styrene (SBS) block co-polymer,styrene-ethylene-butadiene-styrene (SEBS), polyacrylate,acryl-copolymer, ethylene vinyl acetate, polyamide, polyester,polyurethane, polyimide, silane terminated polyolefin, silane terminatedpolyether and silane terminated polyurethane; and b) a stabilizercomposition comprising or consisting of two or three of components (A),(B) and (C), wherein (A) is a specific sterically hindered amine (HALS),(B) is a polymeric sterically hindered amine (HALS), and (C) is aspecific sterically hindered phenol.

The present invention also pertains to a method of stabilizing a hotmelt adhesive against degradation by one or more of light, oxygen andheat, comprising the following steps: providing one or more hot meltadhesive materials selected from the group consisting of polyolefinssuch as amorphous poly-alpha-olefins, metallocene based polyolefins,styrene-isoprene-styrene (SIS) block co-polymer,styrene-butadiene-styrene (SBS) block co-polymer,styrene-ethylenebutadiene-styrene (SEBS), polyacrylate, acryl-copolymer,ethylene vinyl acetate, polyamide, polyester, polyurethane, polyimide,silane terminated polyolefin, silane terminated polyether and silaneterminated polyurethane, silane terminated polyacrylate and adding astabilizer composition as defined herein.

The present invention further pertains to the use of a stabilizercomposition as defined herein for stabilizing a hot melt adhesiveagainst degradation by one or more of light, oxygen and heat, whereinthe hot melt adhesive material is selected from polyolefins such asamorphous poly-alpha-olefins, metallocene based polyolefins,styrene-isoprene-styrene (SIS) block co-polymer,styrene-butadiene-styrene (SBS) block co-polymer,styrene-ethylene-butadiene-styrene (SEBS), polyacrylate,acryl-copolymer, ethylene vinyl acetate, polyamide, polyester,polyurethane, polyimide, silane terminated polyolefin, silane terminatedpolyether, silane terminated polyacrylate and silane terminatedpolyurethane.

Hot melt adhesive (HMA), also known as hot glue, is a form ofthermoplastic adhesive that is supplied in different forms ranging fromsolid cylindrical sticks of various diameters up to pillows or blocks insiliconized paper, designed to be melted in an electric hot glue machine(i.e. melting pots, heated ring mains, guns etc). The application deviceuses a continuous-duty heating element to melt the plastic glue, whichmay be pushed through a gun by a mechanical trigger mechanism, ordirectly by the user. The glue squeezed out of the heated nozzle isinitially hot enough to achieve low enough viscosity to wet the surfaceappropriately. The glue is tacky when hot, and solidifies in a fewseconds to one minute. Hot melt adhesives can also be applied by slotdies, curtain coating or spraying. There are also hot melt adhesivesthat maintain their tackiness after dispensing even at room temperature.Those hot melts are commonly referred to as hot melt pressure sensitiveadhesives (HM-PSA)

Hot melt adhesives have long shelf life and usually can be used afterprolonged period of storage. Some of the disadvantages involve thermalload of the substrate, limiting use to substrates not sensitive tohigher temperatures, and loss of bond strength at higher temperatures,up to complete melting of the adhesive. This can be reduced by using areactive adhesive that after solidifying undergoes further curing e.g.,by moisture (e.g., reactive urethanes and silanes), or is cured byultraviolet radiation.

Hot melt glues usually comprise a composition with various additives.The composition is usually formulated to have a glass transitiontemperature (differentiating the glassy from the rubbery state) belowthe lowest service temperature and a suitably high melt temperature aswell. The degree of crystallization determines the open time of theadhesive. The melt viscosity and the crystallization rate (andcorresponding open time) can be tailored for the application. Highercrystallization rate usually implies higher bond strength. Some polymerscan form hydrogen bonds between the chains, forming pseudo-cross-linksstrengthening the polymer. Other polymers form pseudo cross linksbetween blocks of similar nature such as SBS or SIS.

The nature of the polymer, tackifier, resin and additive influences thenature of mutual molecular interaction and interaction with thesubstrate. Polar groups, hydroxyls and amine groups can form hydrogenbonds with polar groups on substrates like paper or wood or naturalfibers.

Nonpolar polyolefin chains interact well with nonpolar substrates. Goodwetting of the substrate is essential for forming a satisfying bondbetween the adhesive and the substrate. More polar compositions tend tohave better adhesion due to their higher surface energy. Thedistribution of molecular weights and degree of crystallinity influencesthe width of melting temperature range. Polymers with crystalline naturetend to be more rigid and have higher cohesive strength than thecorresponding amorphous ones, but also transfer more strain to theadhesive-substrate interface. Higher molecular weight of the polymerchains provides higher tensile strength and heat resistance. Presence ofunsaturated bonds makes the adhesive more susceptible to autoxidationand UV degradation and necessitates use of antioxidants and stabilizers.

Increase of bond strength and service temperature can be achieved byformation of cross-links in the polymer after solidification. This canbe achieved by using polymers undergoing curing with residual moisture(e.g., reactive polyurethanes, silicones), exposition to ultravioletradiation, electron irradiation, or by other methods.

Some of the possible base materials of hot-melt adhesives include thefollowing:

Polyolefins (PO) (polyethylene (usually LDPE but also HDPE; HDPE hashigher melting point and better temperature resistance), atacticpolypropylene (PP or APP), polybutene-1, oxidized polyethylene, etc.)provide very good adhesion to polypropylene, good moisture barrier,chemical resistance against polar solvents and solutions of acids,bases, and alcohols. Polyolefins have low surface energy and providegood wetting of most metals and polymers. Polyolefins made bymetallocene catalyzed synthesis have narrow distribution of molecularweight and correspondingly narrow melting temperature range. PE and APPare usually used on their own or with just a small amount of tackifiers(usually hydrocarbons) and waxes (usually paraffins or microcrystallinewaxes. Polybutene-1 and its copolymers are soft and flexible, tough,partially crystalline, and slowly crystallizing with long open times.The low temperature of recrystallization allows for stress releaseduring formation of the bond.

Amorphous polyolefin (APO/APAO) polymers are compatible with manysolvents, tackifiers, waxes, and polymers; they find wide use in manyadhesive applications. APO hot melts have good fuel and acid resistance,moderate heat resistance, are tacky, soft and flexible, have goodadhesion and longer open times than crystalline polyolefins. APOs tendto have lower melt viscosity, better adhesion, longer open times andslow set times than comparable EVAs. Some APOs can be used alone, butoften they are compounded with tackifiers, waxes, and plasticizers(e.g., mineral oil, poly-butene oil). Examples of APOs include amorphous(atactic) propylene (APP), amorphous propylene/ethylene (APE), amorphouspropylene/butene (APB), amorphous propylene/hexene (APH), amorphouspropylene/ethylene/butene.

Styrene block copolymers (SBC), also called styrene copolymer adhesivesand rubber-based adhesives, have good low-temperature flexibility, highelongation, and high heat resistance. They are frequently used inpressure-sensitive adhesive applications, where the composition retainstack even when solidified; however non-pressure-sensitive formulationsare also used. They usually have A-B-A structure, with an elastic rubbersegment between two rigid plastic endblocks. The A-B-A structurepromotes a phase separation of the polymer, binding together theendblocks, with the central elastic parts acting as cross-links; thusSBCs do not require additional cross-linking. Styrene-butadiene-styrene(SBS) polymers are used in high-strength PSA applications.Styrene-isoprene-styrene (SIS) polymers are used in low-viscosityhigh-tack PSA applications. Styrene-ethylene/butylene-styrene (SEBS) areused in low self-adhering nonwoven applications.

The usual other ingredients of hot melt adhesive include the following:

tackifying resins (e.g., rosins and their derivates, terpenes andmodified terpenes, aliphatic, cycloaliphatic and aromatic resins (C5aliphatic resins, C9 aromatic resins, and C5/C9 aliphatic/aromaticresins), hydrogenated hydrocarbon resins, and their mixtures,terpene-phenol resins (TPR, used often with EVAs). Tackifiers tend tohave low molecular weight, and glass transition and softeningtemperature above room temperature, providing them with suitableviscoelastic properties;

waxes, e.g. microcrystalline waxes, fatty amide waxes or oxidizedFischer-Tropsch waxes, increase the setting rate. One of the keycomponents of formulations, waxes lower the melt viscosity and canimprove bond strength and temperature resistance;

plasticizers (e.g., benzoates such as 1,4-cyclohexane dimethanoldibenzoate, glyceryl tribenzoate, or pentaerythritol tetrabenzoate,phthalates, paraffin oils, polyisobutylene, chlorinated paraffins,etc.);

antioxidants and stabilizers (e.g. hindered phenols, phosphites,phosphates, hindered aromatic amines). These compounds protect thematerial from thermal degradation and degradation by ultravioletradiation both during service life, compounding and in molten stateduring application.

Current selection of antioxidants for hot melt adhesives is largelyleveraged from plastics application as can be seen when technical datasheets of well-known Irganox® blends are listed, which are applicablefor adhesive application. However, for hot melt adhesives (HMA)application the base polymers are combined with tackifiers and oil forpressure sensitive adhesives (PSA) or wax for non-PSA application.

The stabilization chosen only by the base polymer is not giving optimalresults for hot melt adhesives. Typically the selection of stabilizersis driven by the base polymer which is giving to little attention totackifier and waxes which are important for the adhesion and applicationwindow. Especially for those hot melt adhesives where there is a trendto lower application temperatures like metallocene based polyolefin(mPO) HMA the selection of plastic stabilizers is not appropriate. Withapplication temperatures going down from 170° C. to 150° C. or less theclassical secondary stabilization with phosphites are no longer actingsynergistically. The same trend is also observable for acrylic hot meltpressure sensitive adhesives (HM-PSA) where application temperatures canbe as low as 120° C.

Therefore, it is an object of the present invention to identifyradical-scavenger combinations that are working synergistically alreadyat lower temperatures and take account of the stabilization of thetackifier and the extenders like oil or wax at the same time.

It has been found that the combination of hindered amine lightstabilizers (HALS) with hindered phenols is working particularly wellfor the stabilization of HMAs.

Accordingly, in a first aspect the present invention relates to a hotmelt adhesive comprising

-   -   a) one or more hot melt adhesive materials selected from the        group consisting of polyolefins such as amorphous        poly-alpha-olefins, metallocene based polyolefins,        styrene-isoprene-styrene (SIS) block co-polymer,        styrene-butadiene-styrene (SBS),        styrene-ethylene-butadiene-styrene (SEBS) block co-polymer,        polyacrylate, acryl-copolymer, ethylene vinyl acetate,        polyamide, polyester, polyurethane, polyimide, silane terminated        polyolefin, silane terminated polyether and silane terminated        polyurethane; and    -   b) a stabilizer composition comprising or consisting of two or        three of components (A), (B) and (C), wherein        -   (A) is a sterically hindered amine (HALS) selected from the            group consisting of:

-   -   -   (B) is a polymeric sterically hindered amine (HALS) selected            from the group consisting of:

-   -   -   (C) is a sterically hindered phenol selected from the group            consisting of:

In a preferred embodiment, the stabilizer composition as describedherein comprises or consists of components (A) and (C). In thisembodiment, the weight ratio between components (A) and (C) preferablyis between 1:5 and 5:1.

In another preferred embodiment, the stabilizer composition as describedherein comprises or consists of components (B) and (C). In thisembodiment, the weight ratio between components (B) and (C) preferablyis between 1:5 and 5:1.

In a further preferred embodiment, the stabilizer composition asdescribed herein comprises or consists of components (A), (B) and (C).In this embodiment, the weight ratio between components (A), (B) and (C)preferably is between 8:1:1 and 1:8:1 and 1:1:8.

Preferably, component (A) is selected from the group consisting of:A-(I), A-(II), A-(III), A-(V), A-(VII), A-(IX), A-(X).

Even more preferably, component (A) is selected from the groupconsisting of: A-(I), A-(III).

Preferably, component (B) is selected from the group consisting of:B-(II), B-(III), B-(IV), B-(V), B-(VI).

Even more preferably, component (B) is selected from the groupconsisting of: B-(II), B-(IV).

Preferably, component (C) is selected from the group consisting of:C-(I), C-(II), C-(III), C-(IV), C-(V), C-(VI), C-(VII), C-(VIII),C-(IX), C-(X), C-(XI), C-(XII), C-(XIII), C-(XIV).

Even more preferably, component (C) is selected from the groupconsisting of: C-(III), C-(IV), C-(V), C-(XII), C-(XIV).

In a preferred embodiment the hot melt adhesive according to the presentinvention comprises metallocene based polyolefins as one or more hotmelt adhesive materials.

In an embodiment the hot melt adhesive according to the presentinvention does not comprise a branched polyurethane-polyacrylate resincontaining silicon resin, a branched polyurethane-silicon containingpolyacrylate resin or a branched polyurethane-polyacrylate resin.

Preferably, the stabilizer composition further comprises one or moreadditives selected from the group consisting of: phosphite such asIrgafos 12 CAS 80410-33-9, 2,2′,2″-Nitrilo[triethyltris[3,3,5,5-tetra-tert.-butyl-1,1-biphenyl-2,2diyl]]phosphite, Irgafos 38 CAS 145650-60-8Bis(2,4-di-tert.-butyl-6-methylphenyl)-ethyl-phosphite, Irgafos 126 CAS26741-53-7 Bis-(2,4-ditert.-butylphenol)pentaerythritol diphosphite,Irgafos 168 CAS 31570-04-4 Tris(2,4-di-tert.butylphenyl)phosphite,Irgafos P-EPQ CAS 119345-01-6Tetrakis(2,4-di-tert-butylphenyl)[1,1-biphenyl]-4,4′-diylbisphosphonite,Irgafos TNPP CAS 26523-78-4 Tri-(nonylphenol)-phosphite thioether suchas Irganox PS 800 CAS 123-28-4 Didodecyl-3,3′-thiodipropionate, Irgafos802 CAS 693-36-7 3,3′-Thiodipropionic acid dioctadecylester, secondaryarylamine such as Irganox 5057 CAS 68411-46-1 Benzenamine, N-phenyl-,reaction products with 2,4,4-trimethylpentene, hydroxyl-amine basedstabilizers such as Irgastab FS 042 Oxidized bis(hydrogenated tallowalkyl)amines, optical brighteners such as Tinopal OB CO CAS7128-64-5,5-thiophenediylbis(5-tert-butyl-1,3-benzoxazole), UV-absorbersuch as from the class of benzophenones, cyanoacrylate, formamidine,oxanilide, benzotriazols, hydroxphenyltriazines and inorganicstabilizer.

In a further aspect, the present invention relates to a method ofstabilizing a hot melt adhesive against degradation by one or more oflight, oxygen and heat, comprising the following steps:

-   -   providing one or more hot melt adhesive materials selected from        the group consisting of polyolefins such as amorphous        poly-alpha-olefins, metallocene based polyolefins,        styrene-isoprene-styrene (SIS) block co-polymer,        styrene-butadiene-styrene (SBS),        styrene-ethylenebutadiene-styrene (SEBS) block co-polymer,        polyacrylate, acryl-copolymer, ethylene vinyl acetate,        polyamide, polyester, polyurethane, polyimide, silane terminated        polyolefin, silane terminated polyether and silane terminated        polyurethane, silane terminated polyacrylate and    -   adding a stabilizer composition as defined herein.

In an even further aspect, the present invention relates to the use of astabilizer composition as defined herein for stabilizing a hot meltadhesive against degradation by one or more of light, oxygen and heat,wherein the hot melt adhesive material is selected from polyolefins suchas amorphous poly-alpha-olefins, metallocene based polyolefins,styrene-isoprene-styrene (SIS) block co-polymer,styrene-butadiene-styrene (SBS), styrene-ethylene-butadiene-styrene(SEBS) block co-polymer, polyacrylate, acryl-copolymer, ethylene vinylacetate, polyamide, polyester, polyurethane, polyimide, silaneterminated polyolefin, silane terminated polyether, silane terminatedpolyacrylate and silane terminated polyurethane.

The present invention is further described by the following non-limitingexamples.

Hot Melt Formulations

All materials in the following sections are added to a kneader at roomtemperature (RT, 25° C.). The kneader is closed and evacuated to 0.1mbar. After that the temperature of the kneader is raised from roomtemperature to 155° C. At a temperature of 120° C. the kneading isstarted and continued for 0.5 Hrs.

TABLE 1 Metallocene based Polyolefin HMA Raw Type of 138281 140581.1140581.2 Material Material Supplier Wt % Wt % Wt % Affinity GAMetallocene Dow 33.3 33.3 33.3 1950 Polyolefin Plastomer EastotacHydrogenated Exxon 33.3 33.3 33.3 130 R Hydrocarbon Resin CatenexParaffin Oil Shell 33.3 S 523 Paraflint H1 Paraffin Wax Sasol 33.3 LuwaxPE Paraffin Wax BASF 33.3 10 M Total 100 100 100 Wt % = Weight percent

TABLE 2 SIS based HM-PSA Raw Type of 140525 141150 142492 MaterialMaterial Supplier Wt % Wt % Wt % Kraton D-1102 Linear Kraton 25 SBS/SBPolymer Kraton D SIS, linear Kraton 40 44 1161 PT triblock Sylvalite RERosin Ester Arizona 44 85 L Foral 85 E Hydrogenated Eastman 25 RosinEster Escorez 5300 Cycloaliphatic Exxon 50 hydrocarbon resin Eastotac HHydrogenated Eastman 25 130 R Hydrocarbon Resin Catenex Oil paraffin oilShell 10 12 S 523 Luwax PE Paraffin wax BASF 25 10 M Total 100 100 100

Materials Used:

Raw Material Supplier Description Affinity GA 1950 Dow PolyolefinPlastomer (PO) produced via INSITE ™ technology from Dow Plastics.Density = 0.855 g/cc, MFi = 500 Eastotac 130 R Eastman Eastotac ™ H-130Ris a hydrogenated hydrocarbon resin, having a ring and ball softeningpoint of 130° C. and a molten Gardner color of 4. Catenex S 523 ShellShell Catenex oil is a paraffinic process oil manufactured via solventextraction process with a refractive index of (ASTM D 1218) of 1,478Paraflint H1 Sasol Synthetic wax made by the Fischer-Tropsch processwith a congealing point 208° F. Possesses similar structure to paraffinwax, higher melting point, hardness and molecular weight. Used in hotmelt adhesives LuwaxPE 10 M BASF Polyethylene wax based on ethylenecopolymer that contains acidic groups, melting point (DSC) 110-118° C.Kraton D-1102 Kraton Kraton D1102 K is a clear, linear triblockcopolymer based on styrene and butadiene, with a polystyrene content of28% and a Solution Viscosity (BAM 922) of cps 1100 Kraton D 1161 PTKraton Kraton ® D-1161 polymer is a clear linear triblock copolymerbased on styrene and isoprene, with bound styrene of 15% mass. Melt flowrate 200° C./5 kg (ISO 1133) 9 g/10 min Foral 85-E Eastman HydrogenatedRosin Ester with a softening point of 80- 88° C. (Hercules Drop method)and a melt viscosity of 340 mPas at 140° C. Eastotec H-130R EastmanEastotac ™ H-130R is a hydrogenated hydrocarbon resin, having a ring andball softening point of 130° C. and a molten Gardner color of 4. Escorez5300 Exxon Escorez 5300 is a water white cycloaliphatic hydrocarbonresin Mobile with a glass transition temp, of 55° C. Sylvalite RE 85 LArizona SYLVALITE ® RE 85L RESIN is a polyol ester of rosin with asoftening point, Ring & Ball, ° C. 83-87° C. EVA 2075.1 BuehnenCommercially available Ethyl-Vinyl-Acetat Hot Melt; water clear.

Stabilizer Compositions

TABLE 3 Stabilizer compositions 139485 Std. Cmp. Cmp. Cmp. Cmp Cmp. Inv.Inv. Inv. Inv. Exp. Compound 0 1 2 3 4 5 6 7 8 9 of formula Material phrphr phr phr phr phr phr phr phr phr C-(IV) Irganox 1010 0 0.5 0.25 C-(V)Irganox 1076 0 0.5 0.1 0.2 0.3 0.4 A-(I) Tinuvin 770 0 0.4 0.3 0.2 0.12:1 Mix Irganox B 215 0 0.5 C-(IV)/ Irgafos 168 1:1 Mix Irganox B 225 00.5 C-(IV)/ Irgafos 168 Std. = Standard for this experiment pool, i.e.without stabilization Cmp. = Comparative Example Inv. = InnovativeExample Exp. = Experiment Number Phr = parts per hundred resin

TABLE 4 Stabilizer compositions 140622 Std. Cmp. Cmp. Inv. Inv. Inv.Exp. Compound 0 1 2 3 4 5 of formula Material phr phr phr phr phr phrB-(II) Tinuvin 622 SF 0 0.3 A-(I) Tinuvin 770 0 0.15 0.15 0.1 C-(III)Irganox 1035 0 0.3 0.15 0.1 C-(XII) Irganox 1726 0 0.15 0.1

TABLE 5 Stabilizer composition 141305 Std. Cmp. Cmp. Cmp. Cmp Inv. Inv.Inv. Exp. Compound 0 1 2 3 4 5 6 7 of formula Material phr Phr phr phrphr phr phr phr C-(V) Irganox 1076 0.3 C-(III) Irganox1035 1 0.3 0.3C-(XIV) Irganox 565 1 B-(II) Tinuvin 622 SF 1 0.3 B-(IV) Chimasorb 9440.3 0.3 Irgafos 168 0.3 0.3 0.3 Irganox PS 800 1

TABLE 6 Stabilizer composition 142823 Std. Cmp Cmp Cmp Cmp Inv. Inv.Inv. Inv. Inv. Exp. Compound 1 2 3 4 5 6 7 8 9 of formula Material 0 phrphr phr phr phr phr phr phr phr A-(I) Tinuvin 770 0.6 0.2 0.2 0.2 0.20.3 B-(II) Tinuvin 622 0.6 0.2 0.2 0.2 B-(IIV) Chimasorb 944 0.6 C-(iV)Irganox 1010 0.6 0.2 0.3 C-(V) Irganox 1076 0.4 0.2 C-(III) Irganox 10350.2

TABLE 7 Stabilizer Composition 142523 Std. Cmp. Cmp. Cmp. Inv. Inv. Inv.Exp. Compound 0 1 2 3 4 5 6 of formula Material phr phr phr phr phr phrphr A-(I) Tinuvin 770 0.5 0.5 0.33 0.33 B-(II) Tinuvin 622 0.5 0.33 0.33C-(III) Irganox 1035 0.33 C-(IV) Irganox 1010 0.5 C-(V) Irganox 1076 0.50.5 0.33 Irgafos 168 0.5 Irganox PS 800 0.5

TABLE 8 Stabilizer Composition 140747 Std. Cmp. Cmp. Cmp. Cmp. Cmp. Inv.Inv. Exp. Compound 0 1 2 3 4 5 6 7 of formula Add phr phr phr phr phrphr phr phr B-(II) Tinuvin 622 33.3 33.3 C-(XII) Irganox 1726 1 66.633.3 66.6 C-(V) Irganox 1076 1 0.5 C-(III) Irganox 1035 33.3 Irgafos 16833.3 66.6 0.5 33.3

TABLE 9 Stabilizer Composition 147802 Null B 900 Inv. Nr. 0 5  6 Irganox1076 0 20% 60% Irgafos 168 0 80% Tinuvin 770 40

Test Results

The hot melt formulation is prepared using a sigma-blade kneader.Tackifier, resins and oil or wax are placed in the 150 ml chamber of a“Werner & Pfleiderer” kneader (Type LUK 025). The kneader is evacuatedand heated up. The kneader is started at a temperature of 100° C. with100 rpm. When a temperature of 165° C. is reached kneading is continuedfor further 30 min.

Tests are performed according to ASTM D 4499 (DIN EN ISO 10363). Resultsare given in Gardner color number index acc. ASTM D-6166. Higher numbersmean higher color, i.e. higher oxidation. The effectiveness of astabilizer package can be ranked by the color number. Keeping lowernumbers for a longer time mean better effectiveness of the radicalscavenger package.

The adhesion is tested using a probe tack tester (Testing Machines Inc.,machine 80-02-01) according to ASTM D2979-95 (DIN 55405). Higher gramvalue means higher tack and is preferred.

The viscosities are measured using a CAP 2000+ Viscometer (Brookfield)according to ASTM D 3236. Higher remaining values after the temperatureaging means lesser damage to the polymer and is preferred.

Results of Stabilizations

TABLE 10 Results of stabilizing formulation 138281 with stabilizercompositions 139485 Exp. Hrs. 0 1 2 3 4 5 6 7 8 9 0 5 5 5 5 5 5 5 5 5 58 12 12 12 16 16 17 7 7 7 7 24 18 18 18 18 18 18 13 13 12 14 32 14 15 1415 40 16 16 16 18 48 17 17 18 56 18 18 18 Hrs. = Hours at 177° C.according to ASTM D 4499 (Cycle I) Exp. = Experiment number

TABLE 11 Results of stabilizing formulation 140581.1 with stabilizercompositions 140622 Exp. Hrs. 0 1 2 3 4 5 0 5 5 5 5 5 5 8 12 11 15 11 1012 16 17 16 17 14 12 15 24 18 18 18 15 15 17 32 17 16 18 40 18 18

TABLE 12 Results of stabilizing formulation 140581.2 with stabilizercompositions 140622 Exp. Hrs. 0 1 2 3 4 5 0 3 3 3 3 3 3 8 10 9 14 10 613 16 15 14 17 13 13 14 24 16 16 18 13 16 15 32 17 17 17 14 18 16 40 1818 18 16 17 48 18 18

TABLE 13 Results of stabilizing HMA-formulation 138281 with stabilizercompositions 142823 Exp. Hrs. 0 1 2 3 4 5 6 7 8 9 0 5 5 5 5 5 5 5 5 5 58 16 13 14 14 12 12 11 12 12 10 16 18 16 18 18 16 16 15 16 16 12 ProbeTack [gr] 115 0 0 0 61 120 276 412 311 186 (after 16 hrs) Viscosity[mPas] 655 593 688 668 673 783 705 795 715 766 (after 16 hrs)

TABLE 14 Results of stabilizing HM-PSA formulation 140525 withstabilizer compositions 140747 Exp. Hrs. 0 1 2 3 4 5 6 7 0 3 3 3 3 3 3 33 4 18 14 15 16 16 17 13 13 8 18 18 18 18 18 17 16 12 18 Surface SkinSkin Skin

TABLE 15 Results of stabilizing HM-PSA formulation 141150 withstabilizer compositions 141305 Exp. Hrs. 0 1 2 3 4 5 6 7 0 10 8 8 8 8 88 8 8 16 11 13 18 15 14 14 16 24 18 18 17 17 16 16 17 30 18 18 17 17 17

TABLE 16 Results of stabilizing HM-PSA formulation 142492 withstabilizer composition 142523 Exp. Hrs. 0 1 2 3 4 5 6 0 8 8 8 8 8 8 8 210 10 10 10 10 10 10 8 13 13 13 13 13 13 13 18 18 18 18 18 18 18 18 Tack[gr] 0 0 0 0 116 275 178 (after 18 hrs)

TABLE 17 Results of stabilizing commercial EVA-HMA 2075.1 withstabilizer composition 147802 Exp. Hrs 0 5 6 0 1 1 1 8 6 4 5 16 13 10 8

1: A stabilized hot melt adhesive, comprising a) one or more hot meltadhesive materials selected from the group consisting of a polyolefin, astyrene-isoprene-styrene block copolymer, a styrene-butadiene-styreneblock co-polymer, an polyacrylate, a styrene-ethylene-butadiene-styreneacryl-copolymer, an ethylene vinyl acetate, a polyamide, a polyester, apolyurethane, a polyimide, a silane terminated polyolefin, a silaneterminated polyether, and a silane terminated polyurethane; and b) astabilizer composition comprising two or three of components (A), (B)and (C), wherein (A) is a sterically hindered amine selected from thegroup consisting of:

(B) is a polymeric sterically hindered amine selected from the groupconsisting of:

 and (C) is a sterically hindered phenol selected from the groupconsisting of:

2: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises components (A) and (C). 3: Thestabilized hot melt adhesive according to claim 1, wherein a weightratio between components (A) and (C) is between 1:5 and 5:1. 4: Thestabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises components (B) and (C). 5: Thestabilized hot melt adhesive according to claim 4, wherein a weightratio between components (B) and (C) is between 1:5 and 5:1. 6: Thestabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises components (A), (B) and (C). 7: Thestabilized hot melt adhesive according to claim 6, wherein a weightratio between components (A), (B) and (C) is between 8:1:1 and 1:8:1 and1:1:8. 8: The stabilized hot melt adhesive according to claim 1, whereinthe stabilizer composition comprises component (A), which is selectedfrom the group consisting of:

9: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises component (A), which is selected fromthe group consisting of:

10: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises component (B), which is selected fromthe group consisting of:

11: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises component (B), which is selected fromthe group consisting of:

12: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises component (C), which is selected fromthe group consisting of:

13: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition comprises component (C), which is selected fromthe group consisting of:

14: The stabilized hot melt adhesive according to claim 1, wherein thestabilizer composition further comprises one or more additives selectedfrom the group consisting of: a phosphite, a thioether, a secondaryarylamine, a hydroxyl-amine based stabilizer, a UV-absorber and aninorganic stabilizer. 15: A method of stabilizing a hot melt adhesiveagainst degradation by one or more of light, oxygen and heat, the methodcomprising: adding a stabilizer composition to one or more hot meltadhesive materials selected from the group consisting of a polyolefin, astyrene-isoprene-styrene block co-polymer, a styrene-butadiene-styreneblock co-polymer, a polyacrylate, a styrene-ethylenebutadiene-styreneacryl-copolymer, an ethylene vinyl acetate, a polyamide, a polyester, apolyurethane, a polyimide, a silane terminated polyolefin, a silaneterminated polyether, and a silane terminated polyurethane, wherein thestabilizer composition comprises two or three of components (A), (B) and(C), where (A) is a sterically hindered amine selected from the groupconsisting of:

(B) is a polymeric sterically hindered amine selected from the groupconsisting of:

(C) is a sterically hindered phenol selected from the group consistingof: